调控mTOR-自噬信号通路在血管紧张素II诱导心衰后心房重构、房颤发生中的作用及其机制

Severe atrial remodeling could be identified in the patient with Atrial fibrillation (AF) and Heart failure (HF), which predicts a poor outcome by current medical therapies. Autophagy is a novel and important regulatory pathway in the course of the pathophysiology of cardiac remodeling, while its role in mechanisms of atrial remodeling and atrial fibrillation occurrence is still unclarified. In our pilot experiment, we observed extensive atrial fibrosis in the appendage for patients with AF and correlated with stimulated autophagy. In the cell model, Angiotensin II (AngII) induced autophagy, the expression of the COL-I/III in atrial fibroblasts was upregulated, as well as reduction of Cx 40/43 expression in atrial myocytes. In this study, we plan to establish the AngII-induced heart failure model in vitro and in vivo, combined with interventions including rapamycin, chloroquine, down/over-express Atg5, and selective blocking of AT1/AT2 receptor. We plan to assess autophagic level, mTOR/p70s6k/4E-BP1 pathway, autophagic flux, fibrosis level, Cx40/43 expression, electrical properties of cardiomyocytes and electrophysiology study, to evaluate the relationships among HF, autophagy, atrial remodeling, and AF susceptibility. This study aims to illustrate the role of autophagy in the mechanism of atrial structural/electrical remodeling and AF in AngII-induced HF model, which helps to find a new insight into the therapy of atrial remodeling and AF occurrence.

心衰合并房颤患者多伴随严重的心房重构，目前治疗效果远不如人意。自噬是近年来发现的心肌重构的一条重要调控通路，但在心房重构和房颤发生中的角色尚不明确。预实验中，我们证实房颤患者心耳组织心房重构和自噬水平均增加；AngII刺激促进自噬激活，伴随成纤维细胞COL-I/III分泌增加，心房肌细胞缝隙连接蛋白Cx40/43降解增加。本研究拟构建AngII致心衰的细胞和在体模型，采用雷帕霉素、氯喹、下调/过表达Atg5基因和AT1/AT2受体阻断等调控，通过检测自噬水平、mTOR/p70s6k/4E-BP1通路、自噬流、纤维化指标、Cx40/43 mRNA和蛋白表达、细胞电传导特性及在体电生理检查等变化，评价心衰模型自噬、心房重构/房颤发生之间的关系。旨在阐明自噬在AngII致心衰后心房重构和房颤发生机制的角色，为延缓心房重构和房颤发生寻找新的靶点。

心房颤动（房颤）是临床上最常见的心律失常之一，可引起心力衰竭和脑卒中，具有很高的致残率。伴随房颤的发生及发展，心房基质进行性改变及心房重构会逐渐加重且难以逆转，这也是房颤经导管消融治疗后易远期复发的原因之一。肾素-血管紧张素系统（RAS）激活可促进血管紧张素II（AngII）分泌并作用于心房局部组织，促进心房重构，引起心房基质改变及电传导异常。近来，对房颤患者心房组织进行基因组分析发现自噬相关基因表达升高，心房组织中自噬相关分子表达升高，提示房颤引起的病理性改变可能与自噬异常有关。.从心脏外科收集32例行人工瓣膜置换手术的患者心房组织及血液，其中窦性心律和持续性房颤各16例。相对于窦性心律者，房颤患者血浆中AngII浓度升高，心房间质胶原沉积显著增加，I/III型胶原表达显著增高，且自噬增强。提取原代小鼠心房成纤维细胞并培养，给与AngII刺激，AngII诱导心房成纤维细胞COLI/III分泌增多，自噬增强；进一步分析增强自噬（雷帕霉素）或者阻断自噬(氯喹，LY294002)，Rapa增强自噬后，COLI/III表达进一步增高，氯喹或者LY294002阻断自噬均能抑制AngII诱导的COLI/III表达增高。动物实验结果显示，AngII灌注组和自噬激活组的，小鼠心脏肥厚、心功能下降，COLI/III表达增高，心腔内电生理检查发现心房有效不应期缩短，房颤诱导发生率增高；而自噬阻断组（3-MA）和坎地沙坦治疗组均可逆转上述改变。.本研究发现并证实了AngII诱导成纤维细胞自噬与其上调分泌胶原、加重心房重构、促进房颤发生的关系，并阐明了具体机制，加深了我们对房颤的理解。